GeezerVison

…ng frame cache

The frame cache in the remote debugging module was storing frame chains
without validating that they reached the base frame. This could happen
when a frame chain was interrupted or when the process state changed
during reading, resulting in incomplete stacks being cached. Subsequent
samples that hit the cache would then produce flamegraphs that didn't
reach the bottom of the call stack.

The fix passes base_frame_addr through to process_frame_chain() which
already has validation logic to ensure the frame walk terminates at the
expected sentinel frame. By enabling this validation in the caching code
path and tracking whether we've confirmed reaching the base frame, we
now only store complete frame chains in the cache. When extending from
cached data, we trust that the cached frames were already validated at
storage time, maintaining the invariant that cached stacks are always
complete.

An integration test using deeply nested generators that oscillate the
stack depth is added to verify that all sampled stacks contain the entry
point function. This catches regressions where incomplete stacks might
be cached and returned.